MARIA DEL PILAR YAG�E, R.N.
Diplomate University of Valladolid and Alfonso X University, Madrid, Spain.

STRUCTURE OF THE HUMAN BRAIN

STRUCTURE OF THE NERVOUS CELLS (NEURONS)ESTRUCTURA DE LAS C�LULAS NERVIOSAS (NEURONAS)

The neurons have a central body (soma) and short prolongations called dendrite as well as a long prolongation called axon.With these 2 prolongations the neurons make coenexions (synapsis) with other neurons.

TRASMISION OF THE NERVOUS EST�MULI

The stimuli or nervous impulses are generated or born in the body (soma) of the neurons and are propagated by the ax�n to a great speed (50 meters by second) .It is something similar to the propagation of the electrical current by a cable.When the axon connects with the dendrits of other neighboring neurons transmits then the MESSAGE originated in the cellular body.

THE NERVOUS SYSTEM IS A NET FORMED BY SEPARATE CELLS

During many years was thought that the human brain was a kind of mesh or neurons net connected in a way permanent and continuous. The Spanish Ram�n and Cajal demonstrated that was not so, but our brain is formed by million of neurons capable of been communicated mutually (sinapsis) but separated one from eachother.

SPACE BETWEEN THE NEURONS (SYNAPSIS)

Currently it is known that between the final part of the ax�n of a neuron and the dendrits of the following neuron there is a space called space synaptic.When the stimulus or nervous impulse that travels by the ax�n arrives to its final part some chemical substances called TRANSMISORS are released and these sunstances are joined or coupled to other substances called RECEPTORS in the dendrits of the neighboring neurons, for thus be able to transmit or to propagate the nervous stimuli of a neuron to the others.

TRANSMITTING AND RECEIVING

In this figure we see 2 different transmitters (one tringular and circular other) being joined or being coupled to their corresponding receptors with same form and size.The receptors are proteinas manufactured to recognize only their specific transmitters.

DESTRUCCI�N OF THE TRANSMITERS

The transmitters poured in the space synaptic that are not joined to the receptors are destruyed (recaptation) that is to say returned to their original point, to the interior of the neuron where they are destroyed by some substances called MAO (monoaminooxidases).

MAIN TRANSMITTORS

THE ACETHYLCHOLINE ONE OF THE MAIN TRANSMITTERS OF THE BRAIN

The acethyilcholine was the first known transmitter.It is one of the principal transmitters of the cerebral cortex that it is a kind of mantle or cap that surrounds our brain where is processed all the necessary information for the most cerebral functions such as the reflexive thought and the memory.A substance called ATROPINE is antagonist of the acethycholine that is to say has some effects and opposed to actions those of the acethytilcholine. Atropine is obtained from a plant (Atropa belladonna) whose extracts were used by Hip�crates to treat some intestinal diseases.

INTOXICATION BY ATROPINE

However the excess of those vegetable extracts of the mentioned plant produces a fatal disease characterized by loss of memory and deterioration of the mental powers, reason for which the father of the nomenclature modern botany Carl Linneo designated to that plant as Atropa belladonna, of the - " Atropos " - the most eldest of 3 scanty, the one which were said that was cutting the thread of the life.

ALZHEIMER'S DISEASE

The fact that the poisoning by atropina, substance opposed to acettylcholine, produces a table of loss of report, disorientation and deterioration of the mental powers, very similar to which is observed in the disease of Alzheimer, and the low levels of acethyilcholine in the brains of the patients expired by this disease, they have led to the conclusion of the fact that the disease of Alzheimer is be due to a deficiency of acethyilcholine.The treatment of this terrible disease seems then very simple: to administered acethyilcholine.But evidently it is not thus because the brain is surrounded of a filter or barrier (hematoencephalic barrier) that prevents that arrival of strange substances from the bood.This is in order to maintain our free brain of toxic substances but at the same time a drawback becuase other substances like the acethycholine can not for this reason reach the brain since it is stopped by this barrier.

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